A conventional refrigeration device used in a container and the like switches between a freezing operation for reducing the temperature of the interior of the container to a set temperature lower than zero degrees Celsius to freeze the cargoes inside the container, and a chilling operation for refrigerating the cargoes inside the container with less cooling capacity than that of the freezing operation.
Patent Literature 1, for example, describes switching between a freezing mode (freezing operation) and a chilling mode (chilling operation) according to the set temperature of the interior of a container. Patent Literature 1 also describes switching between, in the chilling mode, a pull-down operation (pull-down control) for setting the capacity of the cooler at 100% to rapidly converge the temperature of the interior to the set temperature, and a fine capacity adjustment operation (capacity control) for performing PID control on the capacity of the cooler, depending on whether the temperature state of the loaded cargoes (cargoes) to be monitored that are stored in terminal boxes falls within an optimal temperature range close to the set temperature, the terminal boxes being provided at the air outlet opened to the interior and an air suction port opened from the interior.
For example, the chilling operation described in the foregoing prior art switches from the pull-down control to the capacity control when the temperature of the cargoes drops to fall within the optical temperature range close to the set temperature as shown in, for example, FIG. 6A. Therefore, for example, in a case where the interior contains a large number of hot cargoes with fresh produce that emit gas, such as durians, there is a possibility that the temperature of the interior increases unexpectedly rapidly due to the respiration heat generated when the gas is released from the hot cargoes during the transition from the pull-down control to the capacity control. In such a case, if the temperature of the interior is reduced to the set temperature by means of the capacity control with a cooling capacity lower than that of the pull-down control, it takes longer to reduce the temperature of the interior. Furthermore, depending on how much the temperature of the interior increases, the cooling capacity of the capacity control might not be enough to reduce the temperature of the interior to the set temperature.